Field of the Invention
The present invention is broadly concerned with improved petroleum-water emulsion breakers useful in petroleum recovery industry. More particularly, the improved emulsion breakers are in the form of emulsified polyol acrylate polymers having high polymer loadings and low inversion viscosities. The invention also pertains to methods of preparing such emulsion breakers, and uses thereof.
Description of the Prior Art
An important objective of any oil production facility is the separation of water and other foreign materials from the produced crude. The breaking of these crude oil and water emulsions constitutes a challenging aspect in the oil production industry.
During the productive life of an oil or gas well, a stage is reached when water will be co-produced in unacceptable quantities. This water co-exists with the hydrocarbons in the reservoir and generally infiltrates into the hydrocarbon-bearing regions of the formation. Eventually water becomes a part of the production from the wells regardless of the method of recovery. Secondary or tertiary methods are another cause of water encroachment. These methods are employed to increase the amount of petroleum recovered from the reservoirs, and they may involve many different techniques. Some of these require the injection of water or steam into the reservoirs, which further complicates the emulsion problem.
An emulsion is a mixture of two immiscible liquids, one of which is dispersed as droplets in the other. The liquid of emulsion that is broken into droplets is known as the dispersed or internal phase, whereas the liquid surrounding the droplets is called the continuous or external phase. In the petroleum industry, water-in-oil emulsions (often referred to as “regular” emulsions) are the most frequently encountered. However, oil-in-water emulsions (sometimes known as “reverse” emulsions) are also very common.
A number of techniques have been employed for demulsification or breaking of emulsions, including heating, electrical processes of dehydration, mechanical separation equipment, free-water knockouts, and chemical injection. In many instances, chemical injections are preferred inasmuch as the emulsions are resolved more quickly and effectively than by other techniques; moreover, chemical treatments have a wide range of application and are equally adaptable to large- or small-scale operations.
Polymeric DMAEMA (dimethylaminoethylmethacrylate)-sulfuric acid salts have been used as oil-in-water emulsion breakers, i.e., water clarifiers or reverse breakers. See U.S. Pat. No. 4,238,330. However, at concentrations above about 10% of these products in water, the dispersions become too thick to pour and are thus difficult to use, particularly in field applications. Higher polymer concentration products are described in U.S. Pat. No. Re. 28,576. In this reference, a water-in-oil emulsion containing particles of vinyl addition polymer or gum is first created and is then inverted to release the polymer into water as a solution. However, the products of this reference do not provide increased polymer concentration with desirable viscosity properties.
There is accordingly a need in the art for improved emulsion breakers, which contain very high polymer loadings with viscosity values allowing them to be easily used under field conditions.